1. Field of the Invention:
This invention relates to a method of hydroformylating 3-methyl-3-buten-1-ol and analogs thereof and to a method of producing further derivatives using such hydroformylation product.
2. Description of the Prior Art:
It is known that, in producing a hydroformylation product by reacting an olefin with carbon monoxide and hydrogen in the presence of a rhodium compound, a rhodium compound modified by a ligand containing an element belonging to the group V of the periodic table (for example, an organic tertiary phosphine such as triphenylphosphine) is used as said rhodium compound. In this method, the presence of such ligand contributes to improvement in stability of the rhodium-carbonyl complex in the reaction system. Therefore, this method is advantageous, among others, in that the catalyst activity can be maintained for a prolonged period of time and that the reaction can be carried out under milder conditions, namely at relatively low temperature and low pressure; hence, said method is highly useful for commercial purposes (refer to J. Falbe, "Carbon Monoxide in Organic Synthesis", Springer-Verlag, New York, 1970, pages 22-25, for instance).
It is also known that 3-methyl-3-buten-1-ol can be used as the olefin to be hydroformylated with carbon monoxide and hydrogen in the presence of a rhodium compound (e.g. U.S. Pat. Nos. 3,966,827 and 4,263,449). According to the patent specifications, a rhodium compound modified by the above-mentioned organic tertiary phosphine is either essential or recommended as the rhodium compound to be used in the hydroformylation of 3-methyl-3-buten-1-ol. In particular, U.S. Pat. No. 3,966,827 describes that the hydroformylation of 3-methyl-3-buten-1-ol in the presence of a rhodium-carbonyl complex modified by an organic tertiary phosphine gave 2-hydroxy-4-methyl-tetrahydropyran in about 75-91% yields. These patent specifications do not contain any specific description on the hydroformylation of 3-methyl-3-buten-1-ol in the presence of a rhodium compound free from modification by a ligand containing an element belonging to the group V of the periodic table, typically an organic tertiary phosphine.
The hydroformylation of 3-methyl-3-buten-1-ol in the presence of a rhodium compound modified by a ligand containing an element belonging to the group V of the periodic table is very slow in rate of reaction as compared with the hydroformylation of .alpha.-olefins such as propylene and 1-octene in the presence of such rhodium compound. Slow reaction rates make it necessary to use expensive rhodium compounds in larger amounts and further use larger reaction apparatus and therefore the above methods are inadequate as the methods for commercial practice. U.S. Pat. No. 3,966,827 describes to the effect that the residue containing the rhodium carbonyl complex modified by an organic tertiary phosphine, which is obtained after separation of the hydroformylation product, 2-hydroxy-4-methyltetrahydropyran, from the reaction mixture by distillation, can be reused for the subsequent hydroformylation. However, rhodium-carbonyl complexes are relatively unstable against heat even in the presence of organic tertiary phosphines capable of stabilizing the same. Thus, in the step of separating high-boiling 2-hydroxy-4-methyl-tetrahydropyran from the reaction mixture by distillation, the rhodium-carbonyl complexes in such reaction mixture is partly deteriorated (see U.S. Pat. No. 4,238,419) and, further, the catalytic activity of said rhodium-carbonyl complexes lowers due to accumulation of high-boiling byproducts in the distillation residue. It is therefore very difficult, in the practice of said method, to recycle and reuse the rhodium-carbonyl complexes and the catalysts for a long period and in a stable manner. Furthermore, the separation or recovery of said rhodium-carbonyl complexes having lowered activity from the reaction system, which is required in the practice of the above method, is troublesome and hardly efficient when said rhodium-carbonyl complexes have been modified by organic tertiary phosphines.
3-Methylpentane-1,5-diol and .beta.-methyl-.delta.-valerolactone are compounds very useful as raw materials in producing polyurethanes and polyesters, for instance and there is known a method of deriving these compounds from products obtained by the above-mentioned hydroformylation of 3-methyl-3-buten-1-ol.
Thus, the above-cited U.S. Pat. No. 3,966,827 and U.S. Pat. No. 4,263,449 propose that 3-methyl-pentane-1,5-diol be produced by hydrogenating the hydroformylation product from 3-methyl-3-buten-1-ol in the presence of a hydrogenation catalyst. On the other hand, .beta.-methyl-.delta.-valerolactone can be produced by oxidatively dehyrogenating 3-methylpentane-1,5-diol at a temperature of 200.degree. C. in the presence of copper chromite [Refer to Organic Syntheses, Coll. Vol. IV, 677 (1963)]. Therefore, by combining these production methods with the above-mentioned hydroformylation of 3-methyl-3-buten-1-ol, it is possible to produce 3-methylpentane-1,5-diol and .beta.-methyl-.delta.-valerolactone by using 3-methyl-3-buten-1-ol, which is readily available in commercial quantities, as the starting material. However, this series of production processes still has a problem from the practical viewpoint, for example, in that the reaction rate in the preceding hydroformylation of 3-methyl-3-buten-1-ol is very slow. Furthermore, the production of .beta.-methyl-.delta.-valerolactone from 3-methyl-3-buten-1-ol requires a complicated production process since independent three reaction steps, namely hydroformylation of the starting 3-methyl-3-buten-1-ol, the subsequent hydrogenation, and oxidation, are necessary.
In Bull. Chem. Soc. Japan, 35, 986 (1962), it is described that .delta.-valerolactone was obtained by subjecting 2-hydroxytetrahydropyran (namely .delta.-oxyvaleraldehyde) to continuous vapor phase reaction at 220.degree.-230.degree. C. in the presence of copper-zinc oxide, copper chromite or copper chromite-zinc oxide. The present inventors found that the use of 2-hydroxy-4-methyltetrahydropyran in lieu of 2-hydroxytetrahydropyran in this known reaction gives, under the same reaction conditions, .beta.-methyl-.delta.-valerolactone. Therefore, by combining this reaction with the hydroformylation of 3-methyl-3-buten-1-ol, it is possible to produce .beta.-methyl-.delta.-valerolactone by a two-step reaction process starting with 3-methyl-3-buten-1-ol. However, when both 3-methylpentane-1,5-diol and .beta.-methyl-.delta.-valerolactone are desired to be produced from 3-methyl-3-buten-1-ol by using the process just mentioned above, it is necessary to subject the hydroformylation product from 3-methyl-3-buten-1-ol, dividedly in a desired ratio and independently, to the hydrogenation and oxidation steps, respectively. Therefore, for this purpose, three independent reaction steps, namely hydroformylation, hydrogenation and oxidation steps, are required even when the above production process is employed. Thus, there still remains unsolved a difficulty that the production process is necessarily complicated.
It is also possible to produce .beta.-methyl-.delta.-valerolactone by another method, namely by reacting ethyl .beta.,.beta.-dimethylacrylate with carbon monoxide and hydrogen in the presence of a cobalt catalyst [Chemische Berichte, 97, 863 (1964)]. However, this method is inadequate for use for commercial purposes since the separation of the desired .beta.-methyl-.delta.-valerolactone from the reaction mixture containing by-products, such as .beta.,.beta.-dimethyl-.gamma.-butyrolactone, having boiling points close to that of said desired product is not easy and moreover the starting ethyl .beta.,.beta.-dimethylacrylate is relatively expensive.